A Fire and Rescue Service (FRS) is an organisation with responsibility for managing and co-ordinating the response to fires and emergencies within a defined geographical territory, for example a county or a city. An FRS is typically managed by a Chief Fire Officer (CFO), several senior managers at DCFO, ACO and Commander level, divisional officers, station managers, station officers and fire fighters. Fire stations are strategically located throughout the territory so that FRS resources may be deployed in the speediest manner to attend to a fire or other incident. Each fire station may have one or more fire appliances and a number of additional support appliances. In turn, each fire appliance is staffed by a fire crew. Each fire crew is assigned a call sign for the purposes of identification. A busy fire station may have up to three fire crews working the same fire appliance at different times of the day.
A fire appliance 1 (fire truck, fire tender, pumper, and several other names), as shown in FIG. 1, is a motorized vehicle used to transport personnel, water and fire-fighting equipment to the scene of a fire. The fire appliance engine is used to drive the vehicle from the fire station to the scene of the fire. Upon arrival at the scene of the fire, the appliance is parked and the engine transmission is transferred to drive the fire pump, generally though a Power Take Off coupling (PTO). This action is referred to as ‘PTO engage’.
A fire appliance has an internal water tank 4 (typically 1,800 litres capacity), an internal pump 6 is driven by the appliance engine to pressurize the water, hoses 8 to direct the water from the pump to the fire and branches 10 (nozzles) to attach to the end of the hoses 8 to direct water onto the fire as depicted in FIG. 2. A fire crew assigned to a fire appliance consists of a manager (Operational Incident Commander—OIC), a pump operator/driver and several branch operators/branchmen. The OIC or pump operator has access to a number of indicators and controls in the pump bay 16. A number of connections are available in the pump bay 16 to allow for taking in water, utilizing the pump 6 or providing water directly into the appliance tank 4. The pump operator also has local access to the engine speed to modify the PTO rotational speed.
Most water used for fire-fighting in town and city areas comes from the water distribution network through fire hydrants. The fire appliance may connect a hose directly to the fire hydrant or through a relay system with one or more fire appliances when the distance between the fire and the hydrant is large. A water carrier may also be used to ferry water taken from the water distribution system to the scene of the fire. Open source water supplies are used where access to the water distribution network is impracticable. Open source water includes rivers, lakes, the sea, canals, swimming pools, etc. The fire appliance tank is typically re-filled after use (at a fire) by connecting to the water distribution network using a fire hydrant. The water supply from a fire hydrant is pressurized and the fire appliance may not be powered on while the tank is being refilled.
In addition to the delivery of water, fire-fighting foam can also be added to water to increase the fire extinguishing capability of the water being delivered onto the fire. Foam is added to water at various percentages ranging from 0.1% to 6% depending on the type of foam and the accelerants in the fire. Establishing the correct ratio of foam to water is critical for making a foam mixture that is efficient for extinguishing fires.
The number and type of outlets available from a fire appliance depends on the type of pump. A single stage pump will have low pressure (0 to 16 bar pressure) outlets only. The dual stage pump is more typical in the British Isles and has high pressure outlets (25 to 40 bar) in addition to the low pressure outlets. The number of low pressure outlets is usually between two and four though specialist appliances can have six or more. The number of high pressure outlets is usually two, one for each side of the appliance. A newer type of pump is a triple stage pump which has low pressure outlets, high pressure outlets and medium pressure outlets to drive water up a ladder platform to supply large volumes of water through a monitor.
Fire-fighting technology traditionally consists of a pump pressure gauge to assist the pump operator control the delivery of water to one or more branchmen, i.e.: fire-fighters holding the branch at the end of the fire hose and directing water onto the fire. The pressure gauge displays the pump pressure (PP) and the engine speed can be controlled to adjust the pump pressure to obtain a suitable branch pressure. The pump operator must take friction loss and pressure loss due to the branch location into account. Therefore, to achieve the optimum performance of fire fighting branches, and with regard to the safety of branchmen, pump operation requires the estimation of a number of hydraulic losses. These include knowledge of pressure loss through hydraulic friction in hose lines, losses introduced depending on the way the hoses are laid out (bends, etc), static head loss and the characteristics of certain types of equipment such as dividing breeches and inductors. The interaction of all these factors affects the pump operator's ability to estimate and maintain branch pressure(s) appropriate to the type and relative position of equipment in use. Using a simple pressure gauge in this way, estimates of flow rate are determined very approximately, by the mental application of simple formulae, or reference to tables, based on a pressure/flow relationship in the case of a simple type ‘A’ branch of a specific diameter. This principle is not readily applicable to specialized foam equipment, jet/spray branches or monitors of varying complexity.
Thus, the pressure approach is considered an approximation at best and does not guarantee the optimum flow for any given branch. FRS's continually strive to improve the way in which they deliver their service to the public and new technology has been adopted in many areas. Branch technology is continually developing and new branches are designed to work most effectively at specific flow rates. Hence, water delivered onto any fire may not be the most efficient or effective, which could result in outcomes such as incidents taking longer to extinguish, greater run-off of contaminated water entering water courses, more carbon emissions entering the atmosphere due to the fires burning for longer and more resources being required at incidents for water management.
Specifically, pressure-based measurement of branch water has been shown to have a number of fundamental flaws. Firstly, there is no direct way of measuring how much water is being delivered at the branch for any given pressure set at the pump. For example, a pump pressure gauge could be showing 4 bar being delivered by the pump but the branch may not be delivering any water at all (due to a number of reasons such as branch shut-down, debris/vehicles fully restricting hose lines, debris blocking the branch). Secondly, with the pressure driven approach, the same pressure conditions are established at the pump for all branches even though the water flow rate and pressure requirements for each branch may vary widely. It is difficult to create the optimum operating conditions for each branch. Furthermore, there is the requirement, for safety reasons, to establish operating conditions for the branchmen with the lowest operating pressure requirement, thereby limiting the effectiveness of other branchmen and the effectiveness of water usage.
To address some of these issues a number of solutions are outlined in the prior art. U.S. Pat. No. 3,974,879 outlines a system for delivering constant water flow rates to an outlet by adjusting the position of the valve in response to a changes in output pressure of the pump and pressure drop in the hose. KR20050003740 outlines a similar system for a fire truck where the water discharge rate and pressure are controlled to automatically apply in fire situations. JP2004261509 describes a pressure control valve to control the pressure of fire extinguishing fluid sent to a pump for application to the fire. However these approaches do not readily address all problems.
The most efficient solution to these problems has seen the increased use of flow meters on fire pumps. Using the information provided by flow meters, the pump operator can establish the optimum operating conditions for each and every branchmen, i.e.: the correct flow rate and pressure rating for the branch being used by the operator. This greatly enhances the safe working conditions of branchmen. A flow meter shows the number of litres per minute being delivered by the pump and (as water is virtually incompressible) which is the same as the flow actually being delivered at the branch. Placing a flow sensor on the incoming supply pipe work informs the operator of how much water is available for fire-fighting. Having knowledge of the incoming water supply, the pump operator can observe any changes and react accordingly to ensure his branch operators have sufficient water supply, are safe or can take action if conditions merit it, and facilitates the best use of water resources. Any changes to the incoming supply can immediately be identified and reported to the Operation Incident Commander (OIC) who can then adjust his/her fire-fighting strategy accordingly. For example, were the incoming supply to halve in volume, the OIC could withdraw one or more of his fire fighters from potentially dangerous situations.
Many FRS's work their pumps by filling the tank from the hydrant supply (using hydrant pressure to fill the tank) while suctioning water from the tank to deliver the branchmen. One of the pump operator's key tasks is to ensure a continuous supply of water to his branchmen, moreover to ensure water supplies do not run out while extinguishing the fire. Without a clear indication of flow rate of incoming supply and of flow rates being delivered to branchmen, the pump operator does not have the means to properly monitor and therefore control water supplies. The out-going flow rate can exceed the incoming flow rate, eventually leading to the tank running dry and branchmen being left without water in the face of a raging fire.
U.S. Pat. No. 6,085,586 and JP2005230524 describe systems where flow sensors and displays are used to present flow summary flow information to the user. In this way, a user may identify the total flow being delivered to a fire by an appliance. KR100687023 describes an alarm type system that identifies water volume contained in a fire engine tank with a sensor.
The present application is directed at improving prior art flow measurement systems in fire appliances.